<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    ul>li:nth-child(2n) {
      color: red;
    }
    ul>li:nth-child(2n+1) {
      color: green;
    }
    ul>li:nth-child(2) {
      color:pink;
    }
    ul>li:nth-child(-n+2) {
      color:blue;
    }
    .box {
      width: 100px;
      height: 100px;

      border: 50px solid orange;
      border-right-color: transparent;
      border-left-color: transparent;
      border-bottom-color: transparent;
      box-sizing: border-box;
      
      transform: rotate(90deg);
    }
  </style>
</head>
<body>
  <ul>
    <li>1</li>
    <li>2</li>
    <li>3</li>
    <li>4</li>
    <li>5</li>
    <li>6</li>
  </ul>
  <div class="box"></div>
</body>
</html>